1. Field of the Invention
This invention relates to the field of self resealable container closures and particularly concerns a closure or cap which is self-resealing after perforation with a blunt tipped implement such as a laboratory pipette. The invention also concerns improvements in clinical laboratory practices resulting from use of the self resealing container closure in specimen containers used in the collection and handling of medical specimens such as urine specimens.
2. State of the Prior Art
Many vials and containers are available with closures, such as a septum of elastomeric material, which are penetrable by a sharp pointed metal needle such as a hypodermic needle, and which maintain a good seal after being pierced by the needle. Those closures, however, cannot be penetrated with relatively blunt tip ends such as those found on liquid transfer pipettes commonly used in clinical laboratories for transferring specimen liquids such as blood and urine.
No containers are known having an elastomeric septum puncturable by such implements and which is also self-resealing following such puncture in order to restore a sufficiently effective liquid tight seal for safe handling and storage of the remaining specimen material at the clinical laboratory location.
Blood and urine specimens are collected routinely during medical examinations in both outpatient and clinical settings. The individual specimens once collected at the direction of an attending physician is forwarded to a clinical laboratory location which typically is remote from the specimen collection site.
In a typical urine collection procedure, a specimen container is handed to the patient, who then deposits the specimen in privacy. The container vessel may have a screw-on or snap-on cap which may be replaced by the patient after depositing the specimen. The closed container is then handed to a nurse or other medical attendant, who arranges for transfer of the container to the laboratory location. The laboratory location may be in the same building or complex, in the case of a hospital, or may be at a considerable distance across town or even in another city if the specimen was taken at a physician""s private office. In either case, some transport of the specimen container is involved, during which it is important to safeguard the specimen against contamination while avoiding any leakage of the specimen liquid from the container. Both these objectives call for a reliable liquid tight seal between the cap and the container.
When received at the clinical location, the specimen container is transferred to a laboratory technician who draws a sample from the clinical specimen in the container. The sample is then subjected to the analytical procedure requested by the attending physician.
The current practice in clinical laboratories is to draw the analytical sample from the specimen container by means of a single use disposable plastic pipette. This pipette is similar to an eye dropper in that it includes a squeeze bulb attached to the upper end of a holding tube, the lower end of which is drawn out to form an elongated tip portion of reduced diameter terminating in an open tip end. The laboratory technician opens the container by manually unscrewing or otherwise removing the container cap, introduces the tip of the pipette into the open container vessel, immerses the tip in the liquid specimen, and aspirates the analytical sample into the holding tube by squeezing and releasing the bulb of the pipette.
The plastic transfer pipettes normally used for this purpose are intended to be used only once and discarded after that single use to prevent cross contamination of successive specimens processed in the laboratory. In the interest of economy, these pipettes are therefore molded in a relatively flexible, soft thermoplastic material which permits the squeeze bulb to be formed integrally with the holding tube and the drawn out tip. The result is that the tip portion of the pipette is rather flexible and is readily bent sideways. A typical transfer pipette of this type has a holding tube which is 2.5xe2x80x3 in length by approximately xc2xcxe2x80x3 in diameter, a tapering portion approximately 1 and xe2x85x9xe2x80x3 in length at the lower end of the holding tube, terminating in a tip portion 1xe2x80x3 in length and approximately xe2x85x9xe2x80x3 in outside diameter. The tip opening is approximately circular and the tip end is cut square or perpendicular to the longitudinal dimension of the tip portion. At the upper end of the holding tube, the squeeze bulb is approximately 1.25xe2x80x3 in length and about xc2xdxe2x80x3 in diameter. The holding tube portion of the pipette can be squeezed flat between two fingers with little effort, and the thinner tip section can be bent sideways very easily, tending to return to a generally straight original condition when released. The wall of the tip portion at the tip opening is about {fraction (1/32)}xe2x80x3 in thickness. If the pipette is grasped at its mid-portion, along the holding tube portion, and the tip end is pressed against a hard surface, the tip portion of the pipette bends sideways with the application of little manual force applied axially along the pipette and normally to the hard surface. These single use soft plastic transfer pipettes are widely used in clinical laboratories and have proven adequate in regard to economics and functionality for their intended purpose.
Some clinical laboratories prefer to use pipetters with disposable tips. Pipetters are syringe-like devices with a plunger which, when depressed, draws a measured, preset amount of fluid into the barrel to the pipetter through a plastic tip fitted onto the end of the pipetters draw tube. The tip can be ejected from the pipetters by pressing a handle or lever provided for this purpose, without the user touching the tip. A new plastic tip is then fitted onto the pipetter for drawing the next sample, and avoid cross-contamination between successive samples. Such pipetters are widely used in laboratories and are available from many different manufacturers. The disposable plastic tips for the pipetters typically are of elongated conical shape, tapering to a circular tip opening. The open tip end is cut across the long axis of the tip to form a blunt tip end which presents the full thickness of the tip wall transversely to that axis. The open tip end diameter may be about {fraction (3/32)}ds of an inch, with a tip opening of about {fraction (1/32)}nd inch. The length of the disposable tip may be about 3xe2x85x9cths inch and the top end about {fraction (5/16)}ths inch.
The open tip end of a disposable plastic pipetter tip may be of comparable dimension to the open tip end of a single use disposable sampling pipette, the main difference being that the plastic pipetter tip is relatively stiff and does not flex readily sideways when pressed against a firm surface.
Clinical urine samples are processed and analyzed in large numbers, with larger clinical laboratories handling thousands of such samples every day. Currently, each of the specimen containers must be manually opened by laboratory personnel in order to draw the analytical samples. Opening and recapping of many such containers constitutes a substantial component of the total labor involved in processing the clinical specimens at the laboratory. Also, the repetitive motion involved in unscrewing and replacing the caps has been known to stress the hand and wrist of laboratory personnel to the point of disability. Furthermore, the open specimen containers pose a risk of contamination of specimens, contamination of the laboratory environment, loss of specimens through accidental spillage, and possible infection of personnel.
It is therefore desirable to provide a method for handling and processing urine and other liquid medical specimens which eliminates the need for opening and closing the specimen containers at the clinical laboratory location. It is further desirable to accomplish this objective with a minimum of change and disruption to existing equipment, supplies and procedures to which laboratory personnel have grown accustomed. In particular, it is desirable to provide specimen containers which can be accessed without uncapping with either the disposable plastic pipetter tips or the disposable plastic transfer pipettes currently in widespread use.
Once an analytical sample is drawn from the specimen container, the container with the remaining specimen material is either discarded, if no further need for the material is contemplated, or is stored against the possible need for additional future analysis of the remaining specimen material. For this reason, it is also important that the closed specimen container maintain an effective seal against spillage and significant leakage during such handling and storage even after an initial sample has been taken of the liquid contents.
For these and other reasons, improvement is needed in the specimen containers used for this purpose and in the handling of the clinical urine specimens.
In response to the aforementioned need, the present invention provides a self resealing perforable closure adaptable to a wide range of containers. The novel closure has particular application in specimen containers for collecting and transporting medical liquid specimens, particularly urine, blood and other clinical specimen fluids. Also disclosed is a method of handling specimens using the improved container.
The improved specimen container has a container vessel with an open container vessel top, and a container cap which can be manually removably engaged to the container vessel for making a liquid tight closure with the vessel top. The container cap has a septum of elastomeric material selected and configured to be puncturable by the relatively blunt tip of a disposable plastic pipetter tip or by a single use soft plastic laboratory transfer pipette driven with manual force against the septum in order to introduce the tip into the capped container for drawing an analytical sample of the urine specimen. The elastomeric material is further selected and configured to be substantially self-resealing against significant leakage of specimen liquid through the septum following withdrawal of the pipette tip from the punctured septum.
That is, the elastomeric septum of this invention has two main characteristics. One chief characteristic of the elastomeric septum according to this invention is that it is puncturable by tubular sampling implements having relatively blunt open tip ends which cannot pierce the relatively hard rubber septa typically used in the caps of drug vials and on the sterile glass tubes commonly used for drawing clinical blood samples. These hard rubber septa can be pierced with sharp metallic needles, but cannot be punctured with any known plastic tubular sampling implement and in particular cannot be punctured by a disposable plastic pipetter tip nor a disposable soft plastic transfer pipette. In general, the septum of this invention is puncturable by relatively wide diameter liquid sampling instruments, of plastic, metal or other material, which do not have a sharp needle point at the tip of the type used for piercing conventional harder rubber septa. By blunt tip end is meant any tip end which is not cut at a slant to form a sharp needle point.
A second chief characteristic of the novel septum is the septum""s ability to substantially self-reseal following puncture by such a relatively blunt and relatively wide diameter tubular sampling implement, to a resealed condition where the septum is substantially closed against spillage of the container""s contents during normal handling of the specimen container on the laboratory premises following puncture of the septum by a sampling implement.
The container cap may be entirely made of the same resilient material which defines the septum, or the cap may have a rim of relatively hard material with the septum of puncturable resilient material supported in an opening in the cap. The container cap may be configured to make a snap fit or press fit with the container top, or alternatively may be threaded for screwing on the container vessel top, in either case making a liquid tight seal with the container vessel.
In a presently preferred configuration of the self resealing closure the resilient material of the puncturable septum is configured so as to define a relatively thick peripheral portion about a central portion of reduced thickness. The thicker peripheral portion is not readily puncturable by the transfer pipette tip while the portion of reduced thickness can be readily punctured with that tip by application of little or moderate manual force to the sampling implement.
The central portion of reduced thickness of the septum may be a dimpled portion gradually diminishing in thickness from the relatively thick peripheral portion to a minimum thickness. Alternatively, one or more slits may be cut partially through the thickness of the septum in order to define a weakened portion, effectively of reduced thickness which is more readily puncturable by the blunt ended tip of the sampling implement than a remaining relatively thick portion of the septum.
A presently preferred elastomer material for the manufacture of the self-reclosing seal of this invention is a proprietary material commercially available as J-1, and described by its vendor as a mixture of hydrogenated isoprene-propylene. The perforable septa of the self-resealing closures are made by injection molding in conventional machines. This invention is not however restricted to this one material as other elastomers may also be found suitable for purposes of this invention.
This invention also includes an improved method of processing clinical laboratory samples including blood and urine samples, using specimen containers equipped with the self-resealing closure also disclosed herein.
The improved method of collecting and processing urine specimens includes the steps of providing to the specimen donor an improved specimen container according to this invention. The specimen donor deposits a urine specimen in the open specimen container, and the container is closed by replacing the container cap to make a liquid tight seal with the container vessel top. The sealed container with the urine specimen is then conveyed to the laboratory location. There, the tip of a relatively blunt generally tubular sampling implement such as a disposable plastic tip for a pipetter or the tip of a single use soft plastic transfer pipette, is manually pressed against the septum with sufficient force to puncture and penetrate through the septum into the container. An analytical sample of the urine specimen is then drawn into the sampling implement, and the tip of the implement is withdrawn to allow the septum to substantially reseal itself. According to this method, the urine specimen is sampled for analysis without opening the closed specimen container once it has been closed at the specimen collection site. After taking of the analytical sample, the specimen container with the remaining urine specimen material may be placed in cold storage against possible future need for additional analytical samples of the same clinical specimen, or discarded if no further analysis is anticipated.
It should be understood that the advantages described above are not limited to the processing of urine specimens and comparable advantages may be realized by depositing and conveying other biological, medical or otherwise hazardous materials in container equipped with the self-resealing closure of this invention.
The improved specimen container of this invention can also be used advantageously with auto sampling analyzers of the type having one or more metal pipettes for dipping into a liquid specimen in a specimen container, aspirating an analytical sample of the liquid specimen, and transferring the aspirated sample for analysis. In such case, the closed specimen container containing the clinical specimen is submitted to the analyzer for automated puncturing of the septum in the specimen container by the metal pipette without first removing the container cap. After the analyzer automatically withdraws the pipette from the septum, the elastomer material of the septum substantially self-reseals the puncture. As a result, analytical sampling of the clinical specimen is performed by the automated machine without removing the container top from the container vessel. These and other advantages, improvements and features will be better understood by reference to the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.